The subject invention relates generally to racking assemblies for avionic equipment, and more particularly to the proper alignment of electrical connectors associated with such racking assemblies. In the typical avionic racking system, a black box having one or more electrical connectors mounted on its rear surface is secured in a mounting tray. At the rear portion of the tray, there is located a surface mounted parallel to the back of the black box. On this surface are mounted one or more electrical connectors designed to mate with the connectors on the back surface of the black box.
In mounting the black box, maintaining alignment between the black box and tray connectors such that proper mating of connectors occurs has proved a serious and aggravating problem. To date, this problem has persisted without panacea.
With the advent of integrated circuitry and the accompanying increase in the number of contact pins within each electrical connector, the alignment problem has become increasingly critical. Today, it is not uncommon to find such electrical connectors with one hundred or more contact pins. Of course, a similar number of connections must be made to the electrical connector itself from the adjoining electronic circuitry. A misalignment often results in bent connector pins, broken connector shells and bowed support trays. Consequently, an entire airplane may be grounded while the one hundred or more connections are established to a replacement connector.
In the prior art, electrical connectors have been mounted to avionic racking equipment by means of screws. Typically, four mounting holes have been provided on the mounting flange of the electrical connector shell member, corresponding to four holes on the connector mounting plate member to which the connector is to be mounted. The centers of the holes on both the mounting flange and the mounting plate can be closely toleranced to assure a match between the mounting flange holes and the mounting plate holes. Furthermore, the center line of each electrical connector mounted on the avionic tray can be closely toleranced to align with the center line of the connector on the rear of the black box to maintain proper alignment between the corresponding mating connectors. Seemingly, when the screws are inserted in the mounting holes perfect alignment should result.
The problem with this mounting approach of the prior art and the starting point of this invention is the recognition that screws make poor alignment devices. Screws are typically produced by screw machines, and the variations in their size are such that tolerances in the size of the mounting holes are on the order of 0.015 to 0.020 inches. To compensate for the considerable amount of slop movement allowed by these tolerances, mating connectors have been mounted utilizing flexible bushings which provide a float off-center of their associated electrical connector. Such connectors mounted in bushings are typically characterized as "floating" whereas connectors mounted solely by screws are referred to as "hardmounted". Typically, this float off-center in on the order of 0.031 inches. With today's high-density connectors, the off-center play of both the trays and box-mounted connectors has facilitated rather than alleviated improper mating of connectors and consequent damage. Another phenomenon noted is that improper screw alignment in the bushings can result in the associated connector being locked in position or displaced rearwardly such that the hardmounted connector bottoms out and never makes effective electrical contact.